Want to add support for 'gridAttachNextTo' for Grid somehow

[Cj-bc]

First of all, thanks for this library!
It gives me good opportunity and motivation to look into GUI applications.

What I want

I want to use gridAttachNextTo instead of 'gridAttach' so that I don't have to change leftAttach/topAttach manually for each children.
This is neccesary for me because I want to change each width/height in runtime.
If this feature is determined as 'unnecessary' for library, I will keep this just mime.

Suggestion

I'm thinking 2 way:

• Make new widget (e.g. GridNextTo or something like that) that uses 'gridAttachNextTo' in appendChild method of IsContainer
• Add new constructor of GridChildProperties (e.g. GridChildPropertiesNextTo) which contains necessary properties i.e. sibling/side, and use them with gridAttachNextTo in appendChild

Current status (at time I made this issue)

I've tried later one in my fork and seems working fine for limited case.
It doesn't supports 'sibling' feature which is big problem if it will be part of the library.

But I'm not sure how to implement 'sibling' (and also tests are not implemented yet), so I want to get help about this.

Note that I'm willing to change current implementation or throw away it if this functionality could be part of this library.